1. Field of the Invention
This invention relates to an apparatus for gapping an elongate stringer chain at predetermined intervals to be assembled with various slide fastener component parts.
2. Prior Art
Generally, a substantially endless elongated stringer chain comprising a pair of support tapes and rows of coupling elements secured to the respective tapes is cut successively to predetermined lengths to provide individual slide fasteners. Prior to cutting, it has been a common practice to gap the stringer chain to form element-free portions or gaps at predetermined intervals along the inner longitudinal edges of the stringer chain, the gaps being utilized for mounting various slide fastener component parts such as sliders, bottom end stops and top end stops. The element-free portions or gaps of the stringer chain are formed by removing a predetermined number of coupling elements by means of a cutting tool having an operative edge length corresponding to a pre-calculated gap length. For one reason or another, the cutter would leave some of the endmost coupling elements half or partly cut away at either or both of the leading and trailing ends of the gaps, with resultant uncut debris interfering with a subsequent parts applying operation. To eliminate this problem, it has been proposed, as disclosed for example in Japanese Laid-Open Utility Model Publications 53-16713 and 63-31611, to provide a positioning pawl or pin adjacent to each of the leading and trailing ends of a cutter for engaging the coupling elements and thus setting the stringer chain up in position for gapping by the cutter. Since such positioning pawls or pins are spaced apart from each other by a distance greater than the operative length of the cutter, it would often occur that the number of coupling elements actually existing between the respective positioning pawls or pins differs from a predetermined number of coupling elements to be removed to provide gaps of a predetermined length. This discrepancy is believed attributable to changes in the tension exerted longitudinally of the stringer chain during feeding thereof, or dimensional errors of the coupling elements. The resultant gaps therefore would often carry irregularly severed endmost coupling elements differing in shape between those in one row and those in the other row on the respective support tapes, rendering it difficult to fit properly in place such component parts as top and bottom end stops particularly separable end stops.